Energy Barrier Characterization of Trapped Vortices in Superconducting Microstrip Configurations
We present recent progress on the modelling of trapped vortices in superconducting niobium thin films using InductEx. By computing the Gibbs free energy for single-vortex states in microstrip and ground-plane structures, we quantify how temperature, geometry, and applied current impact vortex entry, separation, and motion. Our results show that as the temperature decreases below the critical temperature (Tc), the energy barriers grow significantly, making vortex motion increasingly difficult. Moreover, when a vortex resides in both the microstrip and ground plane, an additional energy barrier emerges from attempts to separate the vortices in the two layers. For the experimentally more common scenario of a vortex trapped solely in the ground plane, we determine the minimum current needed in an overlying microstrip to dislodge the vortex and drive it across the microstrip. This current requirement grows rapidly at lower temperatures, highlighting the challenges of flux management in superconducting circuits operating far below Tc. Finally, variations in microstrip width, isolation-layer thickness, and the presence of moats reveal the impact on energy barriers and vortex dynamics. These insights provide guidance for designing effective vortex control strategies to control vortex behaviour in superconducting circuits, enabling higher integration densities and enhanced operational stability.